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Lazy Loading Code Generator

Write image and iframe markup that loads at the right time.

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Produces a srcset. The filename has the width appended before its extension.

Markup

Your generated code appears here.

Quick Tool Overview

The Lazy Loading Code Generator writes image and iframe markup with the loading and priority attributes set for where the element actually sits. Its main job is preventing the common mistake: lazy loading the hero image delays exactly what Largest Contentful Paint measures, making a Core Web Vitals score worse while feeling like an optimisation.

What it does
Generates image and iframe markup with correct loading attributes
You give it
The image source, dimensions and where it sits on the page
You get back
Markup with loading, fetchpriority, dimensions and optional srcset
Best for
Image-heavy pages and anything with an embedded video or map
SEO Tools Free, unlimited use No sign-up Runs in your browser

About the Lazy Loading Code Generator

Describe the image and the generator writes the markup: native lazy loading where it belongs, eager loading with high fetch priority where it does not, width and height so nothing shifts, a responsive srcset, and a picture element with modern formats if you want one.

The mistake this is really here to prevent is lazy loading the wrong image. Applying loading="lazy" to everything, including the hero, delays the very image that Largest Contentful Paint is measuring, and it is a reliable way to make a Core Web Vitals score worse while believing you improved it. Anything above the fold should load eagerly, and the LCP element should carry fetchpriority="high". Everything below the fold should be lazy. The generator asks which one you are dealing with rather than applying the same attribute to both.

Key features of the Lazy Loading Code Generator

Position decides the attributes

Above the fold loads eagerly, the hero gets high fetch priority, below the fold goes lazy.

Dimensions always set

Width and height are what stop the page jumping, which is the whole of Cumulative Layout Shift.

Responsive sources

A srcset and sizes, or a full picture element with AVIF and WebP sources.

Iframes too

Lazy loading an embedded video or map defers more third-party JavaScript than any image saves.

No library needed

Native loading is supported everywhere current, so the generated markup carries no JavaScript.

How to use the Lazy Loading Code Generator

  1. 1

    Say where the image sits

    Above the fold, below it, or the main hero — each gets different attributes.

  2. 2

    Add the source and dimensions

    Width and height are what stop the page shifting as the image arrives.

  3. 3

    Add responsive sources

    Optional widths become a srcset and sizes, or a picture element with AVIF and WebP.

  4. 4

    Copy the markup

    Paste it in, and check the hero image is not the one you made lazy.

Frequently asked questions

No, and doing so is actively harmful. Anything visible when the page opens should load eagerly, and the largest one should carry fetchpriority="high". Lazy loading the hero delays exactly the image Largest Contentful Paint measures.

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